Where two ends of a cable such as a telecommunications cable are spliced together, the splice area is ordinarily housed within a protective cover known as a closure. Common to substantially all closures is the requirement that they restrict moisture ingress. The integrity of seals which are used to restrict moisture ingress is important especially because of transmission parameters which are readily effected by changes in the moisture content within the cable.
Such closures often have included cylindrical covers with one or more longitudinal joints and end plates that surround incoming and outgoing cables and that form seals with the covers. An example of a prior art closure is shown in U.S. Pat. No. 4,927,227 which issued on May 22, 1990 in the names of W. H. Bensel, III, et al.
To prevent the ingress of moisture, some systems employ dry air, nitrogen or a similar chemically inert gas in the cables and closures. In this type of closure, the gas is pressurized to create a flow from enclosed equipment through any openings and prevent the ingress of moisture. In such a system, it is advantageous to minimize the amount of gas leakage to reduce the consumption of gas needed to maintain adequate pressure throughout the system. Accordingly, closures and associated equipment should be sealed adequately to prevent a reduction in pressure and the loss of gas. Also, cable closures must be sealed to prevent the ingress of moisture.
In U.S. Pat. No. 4,361,721 which issued on Nov. 20, 1982 in the name of John R. Massey, there is disclosed a grommet which is used in splice cases to provide a seal about an entering or exiting cable. The grommet comprises a unitary elastomeric body having a slit along a split line to allow a cable to be inserted into a cable receiving passageway within the grommet. Each passageway is defined by an interior sidewall from which a plurality of longitudinally spaced circumferential ridges extend. For a substantial portion of its circumference, each ridge has an axis of projection which forms an oblique angle with respect to an axis of the passageway and is sufficiently elongated in longitudinal cross section so as to be capable of flexing with respect to the axis of projection during cable insertion and enlarging its opening diameter to accommodate and form a radial seal about a cable being inserted.
Despite such provision as the aforementioned grommet, moisture continues to be observed within closures. Because of the slit in the grommet which allows access to the opening therethrough to facilitate insertion of a cable, portions of the grommet on each side of the slit may become offset from each other as a result of forces being applied to the cable or to the closure. With those portions offset from each other, the portions of the ridges which define the cable opening and which are adjacent to the slit become offset, forming a path therebetween along which gas and/or moisture may travel.
Offset may come about in another way. In some closures, the end plate may be formed to include two portions which are separated along lines which extend through the cable openings. Prior to assembly of the end plate portions, grommets are disposed in the openings in one portion and then the other portion assembled thereto. However, there are some closures in which the end plate is unipartite in which case the grommet or grommets are forced into the opening or openings in the end plate. When this is done, portions of each grommet adjacent to its split line may become offset from each other.
What is needed and what seemingly is not available in the prior art is a cable closure which includes a grommet that maintains its sealing capability notwithstanding the application of expected forces thereto. The sought after grommet should be relatively easy to manufacture and should continue to provide a seal about a cable extending therethrough despite the application of forces which tend to offset portions of the grommet adjacent to the split line.